nx2: run the guest counter at 31.25 MHz for Switch 2 titles

The Switch 2 counter runs at 31.25 MHz and its SDK converts ticks with
that constant: Mario Kart World's sdk builds 31,250,000 in
nn::os::GetSystemTickFrequency, TickManager::ConvertToTimeSpan and
TickManager::ConvertToTick (19.2 MHz appears nowhere). Eglantine counted
at the Switch 1 rate for every title, so every tick-based time in a
Switch 2 game was off by 1.63x: elapsed times read short, and a deadline
of one 60 Hz frame converted to ticks waited ~27 ms.

The wall clock now has a guest counter frequency, set at boot: 31.25 MHz
for Switch 2 programs, 19.2 MHz otherwise, EDEN_NX2_CNTFRQ=<Hz> to force
one. CNTPCT reads, CNTFRQ_EL0, svcGetSystemTick, thread tick counts and
the time services' tick conversions follow it, and the CNTPCT spin
detection keeps its ~1.7 us threshold.

Mario Kart World, title screen and attract demo, 180 s, same build:
frame times unchanged (17-19 ms once warm), process CPU time 848 s
instead of 930 s.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/core/arm/nce/patcher.cpp b/src/core/arm/nce/patcher.cpp
index f21d7cacdc..72c3497f03 100644
--- a/src/core/arm/nce/patcher.cpp
+++ b/src/core/arm/nce/patcher.cpp
@@ -627,7 +627,7 @@ void Patcher::WriteMsrHandler(ModuleDestLabel module_dest, oaknut::XReg src_reg,
 }
 
 void Patcher::WriteCntfrqHandler(ModuleDestLabel module_dest, oaknut::XReg dest_reg, oaknut::VectorCodeGenerator& cg) {
-    cg.MOV(dest_reg, Common::WallClock::CNTFRQ);
+    cg.MOV(dest_reg, Common::g_wall_clock.GetGuestCNTFRQ());
 
     // Jump back to the instruction after the emulated MRS.
     if (&cg == &c_pre)
@@ -642,6 +642,7 @@ void Patcher::WriteCntpctHandler(ModuleDestLabel module_dest, oaknut::XReg dest_
 #else
     static Common::WallClock clock(true, 1);
 #endif
+    clock.SetGuestCNTFRQ(Common::g_wall_clock.GetGuestCNTFRQ());
     const auto factor = clock.GetGuestCNTFRQFactor();
     const auto raw_factor = std::bit_cast<std::array<u64, 2>>(factor);